Double planet

In astronomy, double planet and binary planet are informal terms used to describe a binary system of two astronomical objects that each satisfy the definition of planet and that are near enough to each other to have a significant gravitational effect on each other compared with the effect of the star(s) they orbit. As of 2010, there are no officially classified double planets in our Solar system. One unofficial definition is that the objects orbit a common center of gravity, the barycenter, that is above both their surfaces.[citation needed]Similarly, there are also binary asteroids (also known as double minor planets) such as 90 Antiope, and binary Kuiper belt objects (KBOs) such as (79360) 1997 CS29 and 1998 WW31. The European Space Agency has referred to the Earth–Moon system as a type of double planet.[1] The IAU General Assembly in Au